Answer:
12
Step-by-step explanation:
Let d represent the number of dimes Lily saved. Then the value of her coins in cents is ...
10d +100(16-d) = 520
-90d +1600 = 520 . . . . . eliminate parentheses, collect terms
-90d = -1080 . . . . . . . . . . subtract 1600
d = -1080/-90 = 12 . . . . . divide by the coefficient of d
Lily has 12 ten-cent coins.
The polygon that when rotated at 180 degrees about it's center may not be carried onto itself is a quadrilateral. The reason being quadrilateral is not regular in the sense that different sides have different measures.
Word problem: Today the temperature dropped 13 °F. After this drop, the temperature was 74 °F. What was the original temperature outside before the drop?
Subtraction problem: x °F - 13 °F = 74 °F
Solve: x - 13 = 74
x - 13(+13) = 74 + 13
x = 87 °F